Extension of refocus depth range in digital holographic microscopy

Area of Science:

• Optics and Photonics
• Microscopy Techniques
• Digital Imaging

Background:

• Digital holographic microscopy (DHM) faces limitations in refocus depth range due to microscope objective constraints.
• Extending the refocus depth range is crucial for comprehensive high-resolution imaging in DHM.

Purpose of the Study:

• To investigate the relationship between DHM's refocus depth range and its optical parameters.
• To develop and validate a novel method for significantly extending the refocus depth range in DHM.

Main Methods:

• Theoretical and experimental analysis of DHM optical parameters influencing refocus depth.
• Implementation of a combined approach using wavefront coding, bicubic interpolation, and extrapolation iteration.
• Modification of numerical reconstruction with a propagator kernel and logarithmic phase mask for uniform point spread function.
• Doubling hologram size to enhance refocused image resolution.

Main Results:

• Successfully extended the refocus depth range of DHM from 0.9 mm to 1.5 mm.
• Achieved a uniform point spread function on the refocus plane through numerical reconstruction modifications.
• Demonstrated improved resolution in refocused images via hologram size enlargement.

Conclusions:

• The proposed method effectively extends the refocus depth range in DHM.
• This advancement offers significant guidance for achieving high-resolution imaging over extended depth ranges in DHM applications.